// Copyright 2006 Google Inc.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//   http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.


// Known Issues:
//
// * Patterns only support repeat.
// * Radial gradient are not implemented. The VML version of these look very
//   different from the canvas one.
// * Clipping paths are not implemented.
// * Coordsize. The width and height attribute have higher priority than the
//   width and height style values which isn't correct.
// * Painting mode isn't implemented.
// * Canvas width/height should is using content-box by default. IE in
//   Quirks mode will draw the canvas using border-box. Either change your
//   doctype to HTML5
//   (http://www.whatwg.org/specs/web-apps/current-work/#the-doctype)
//   or use Box Sizing Behavior from WebFX
//   (http://webfx.eae.net/dhtml/boxsizing/boxsizing.html)
// * Non uniform scaling does not correctly scale strokes.
// * Optimize. There is always room for speed improvements.

// Only add this code if we do not already have a canvas implementation
if (!document.createElement('canvas').getContext) {

	(function () {

		// alias some functions to make (compiled) code shorter
		var m = Math;
		var mr = m.round;
		var ms = m.sin;
		var mc = m.cos;
		var abs = m.abs;
		var sqrt = m.sqrt;

		// this is used for sub pixel precision
		var Z = 10;
		var Z2 = Z / 2;

		var IE_VERSION = +navigator.userAgent.match(/MSIE ([\d.]+)?/)[1];

		/**
		 * This funtion is assigned to the <canvas> elements as element.getContext().
		 * @this {HTMLElement}
		 * @return {CanvasRenderingContext2D_}
		 */
		function getContext() {
			return this.context_ ||
				(this.context_ = new CanvasRenderingContext2D_(this));
		}

		var slice = Array.prototype.slice;

		/**
		 * Binds a function to an object. The returned function will always use the
		 * passed in {@code obj} as {@code this}.
		 *
		 * Example:
		 *
		 *   g = bind(f, obj, a, b)
		 *   g(c, d) // will do f.call(obj, a, b, c, d)
		 *
		 * @param {Function} f The function to bind the object to
		 * @param {Object} obj The object that should act as this when the function
		 *     is called
		 * @param {*} var_args Rest arguments that will be used as the initial
		 *     arguments when the function is called
		 * @return {Function} A new function that has bound this
		 */
		function bind(f, obj, var_args) {
			var a = slice.call(arguments, 2);
			return function () {
				return f.apply(obj, a.concat(slice.call(arguments)));
			};
		}

		function encodeHtmlAttribute(s) {
			return String(s).replace(/&/g, '&amp;').replace(/"/g, '&quot;');
		}

		function addNamespace(doc, prefix, urn) {
			if (!doc.namespaces[prefix]) {
				doc.namespaces.add(prefix, urn, '#default#VML');
			}
		}

		function addNamespacesAndStylesheet(doc) {
			addNamespace(doc, 'g_vml_', 'urn:schemas-microsoft-com:vml');
			addNamespace(doc, 'g_o_', 'urn:schemas-microsoft-com:office:office');

			// Setup default CSS.  Only add one style sheet per document
			if (!doc.styleSheets['ex_canvas_']) {
				var ss = doc.createStyleSheet();
				ss.owningElement.id = 'ex_canvas_';
				ss.cssText = 'canvas{display:inline-block;overflow:hidden;' +
				// default size is 300x150 in Gecko and Opera
				'text-align:left;width:300px;height:150px}';
			}
		}

		// Add namespaces and stylesheet at startup.
		addNamespacesAndStylesheet(document);

		var G_vmlCanvasManager_ = {
			init: function (opt_doc) {
				var doc = opt_doc || document;
				// Create a dummy element so that IE will allow canvas elements to be
				// recognized.
				doc.createElement('canvas');
				doc.attachEvent('onreadystatechange', bind(this.init_, this, doc));
			},

			init_: function (doc) {
				// find all canvas elements
				var els = doc.getElementsByTagName('canvas');
				for (var i = 0; i < els.length; i++) {
					this.initElement(els[i]);
				}
			},

			/**
			 * Public initializes a canvas element so that it can be used as canvas
			 * element from now on. This is called automatically before the page is
			 * loaded but if you are creating elements using createElement you need to
			 * make sure this is called on the element.
			 * @param {HTMLElement} el The canvas element to initialize.
			 * @return {HTMLElement} the element that was created.
			 */
			initElement: function (el) {
				if (!el.getContext) {
					el.getContext = getContext;

					// Add namespaces and stylesheet to document of the element.
					addNamespacesAndStylesheet(el.ownerDocument);

					// Remove fallback content. There is no way to hide text nodes so we
					// just remove all childNodes. We could hide all elements and remove
					// text nodes but who really cares about the fallback content.
					el.innerHTML = '';

					// do not use inline function because that will leak memory
					el.attachEvent('onpropertychange', onPropertyChange);
					el.attachEvent('onresize', onResize);

					var attrs = el.attributes;
					if (attrs.width && attrs.width.specified) {
						// TODO: use runtimeStyle and coordsize
						// el.getContext().setWidth_(attrs.width.nodeValue);
						el.style.width = attrs.width.nodeValue + 'px';
					} else {
						el.width = el.clientWidth;
					}
					if (attrs.height && attrs.height.specified) {
						// TODO: use runtimeStyle and coordsize
						// el.getContext().setHeight_(attrs.height.nodeValue);
						el.style.height = attrs.height.nodeValue + 'px';
					} else {
						el.height = el.clientHeight;
					}
					//el.getContext().setCoordsize_()
				}
				return el;
			}
		};

		function onPropertyChange(e) {
			var el = e.srcElement;

			switch (e.propertyName) {
			case 'width':
				el.getContext().clearRect();
				el.style.width = el.attributes.width.nodeValue + 'px';
				// In IE8 this does not trigger onresize.
				el.firstChild.style.width = el.clientWidth + 'px';
				break;
			case 'height':
				el.getContext().clearRect();
				el.style.height = el.attributes.height.nodeValue + 'px';
				el.firstChild.style.height = el.clientHeight + 'px';
				break;
			}
		}

		function onResize(e) {
			var el = e.srcElement;
			if (el.firstChild) {
				el.firstChild.style.width = el.clientWidth + 'px';
				el.firstChild.style.height = el.clientHeight + 'px';
			}
		}

		G_vmlCanvasManager_.init();

		// precompute "00" to "FF"
		var decToHex = [];
		for (var i = 0; i < 16; i++) {
			for (var j = 0; j < 16; j++) {
				decToHex[i * 16 + j] = i.toString(16) + j.toString(16);
			}
		}

		function createMatrixIdentity() {
			return [
      [1, 0, 0], [0, 1, 0], [0, 0, 1]
				];
		}

		function matrixMultiply(m1, m2) {
			var result = createMatrixIdentity();

			for (var x = 0; x < 3; x++) {
				for (var y = 0; y < 3; y++) {
					var sum = 0;

					for (var z = 0; z < 3; z++) {
						sum += m1[x][z] * m2[z][y];
					}

					result[x][y] = sum;
				}
			}
			return result;
		}

		function copyState(o1, o2) {
			o2.fillStyle = o1.fillStyle;
			o2.lineCap = o1.lineCap;
			o2.lineJoin = o1.lineJoin;
			o2.lineWidth = o1.lineWidth;
			o2.miterLimit = o1.miterLimit;
			o2.shadowBlur = o1.shadowBlur;
			o2.shadowColor = o1.shadowColor;
			o2.shadowOffsetX = o1.shadowOffsetX;
			o2.shadowOffsetY = o1.shadowOffsetY;
			o2.strokeStyle = o1.strokeStyle;
			o2.globalAlpha = o1.globalAlpha;
			o2.font = o1.font;
			o2.textAlign = o1.textAlign;
			o2.textBaseline = o1.textBaseline;
			o2.arcScaleX_ = o1.arcScaleX_;
			o2.arcScaleY_ = o1.arcScaleY_;
			o2.lineScale_ = o1.lineScale_;
		}

		var colorData = {
			aliceblue: '#F0F8FF',
			antiquewhite: '#FAEBD7',
			aquamarine: '#7FFFD4',
			azure: '#F0FFFF',
			beige: '#F5F5DC',
			bisque: '#FFE4C4',
			black: '#000000',
			blanchedalmond: '#FFEBCD',
			blueviolet: '#8A2BE2',
			brown: '#A52A2A',
			burlywood: '#DEB887',
			cadetblue: '#5F9EA0',
			chartreuse: '#7FFF00',
			chocolate: '#D2691E',
			coral: '#FF7F50',
			cornflowerblue: '#6495ED',
			cornsilk: '#FFF8DC',
			crimson: '#DC143C',
			cyan: '#00FFFF',
			darkblue: '#00008B',
			darkcyan: '#008B8B',
			darkgoldenrod: '#B8860B',
			darkgray: '#A9A9A9',
			darkgreen: '#006400',
			darkgrey: '#A9A9A9',
			darkkhaki: '#BDB76B',
			darkmagenta: '#8B008B',
			darkolivegreen: '#556B2F',
			darkorange: '#FF8C00',
			darkorchid: '#9932CC',
			darkred: '#8B0000',
			darksalmon: '#E9967A',
			darkseagreen: '#8FBC8F',
			darkslateblue: '#483D8B',
			darkslategray: '#2F4F4F',
			darkslategrey: '#2F4F4F',
			darkturquoise: '#00CED1',
			darkviolet: '#9400D3',
			deeppink: '#FF1493',
			deepskyblue: '#00BFFF',
			dimgray: '#696969',
			dimgrey: '#696969',
			dodgerblue: '#1E90FF',
			firebrick: '#B22222',
			floralwhite: '#FFFAF0',
			forestgreen: '#228B22',
			gainsboro: '#DCDCDC',
			ghostwhite: '#F8F8FF',
			gold: '#FFD700',
			goldenrod: '#DAA520',
			grey: '#808080',
			greenyellow: '#ADFF2F',
			honeydew: '#F0FFF0',
			hotpink: '#FF69B4',
			indianred: '#CD5C5C',
			indigo: '#4B0082',
			ivory: '#FFFFF0',
			khaki: '#F0E68C',
			lavender: '#E6E6FA',
			lavenderblush: '#FFF0F5',
			lawngreen: '#7CFC00',
			lemonchiffon: '#FFFACD',
			lightblue: '#ADD8E6',
			lightcoral: '#F08080',
			lightcyan: '#E0FFFF',
			lightgoldenrodyellow: '#FAFAD2',
			lightgreen: '#90EE90',
			lightgrey: '#D3D3D3',
			lightpink: '#FFB6C1',
			lightsalmon: '#FFA07A',
			lightseagreen: '#20B2AA',
			lightskyblue: '#87CEFA',
			lightslategray: '#778899',
			lightslategrey: '#778899',
			lightsteelblue: '#B0C4DE',
			lightyellow: '#FFFFE0',
			limegreen: '#32CD32',
			linen: '#FAF0E6',
			magenta: '#FF00FF',
			mediumaquamarine: '#66CDAA',
			mediumblue: '#0000CD',
			mediumorchid: '#BA55D3',
			mediumpurple: '#9370DB',
			mediumseagreen: '#3CB371',
			mediumslateblue: '#7B68EE',
			mediumspringgreen: '#00FA9A',
			mediumturquoise: '#48D1CC',
			mediumvioletred: '#C71585',
			midnightblue: '#191970',
			mintcream: '#F5FFFA',
			mistyrose: '#FFE4E1',
			moccasin: '#FFE4B5',
			navajowhite: '#FFDEAD',
			oldlace: '#FDF5E6',
			olivedrab: '#6B8E23',
			orange: '#FFA500',
			orangered: '#FF4500',
			orchid: '#DA70D6',
			palegoldenrod: '#EEE8AA',
			palegreen: '#98FB98',
			paleturquoise: '#AFEEEE',
			palevioletred: '#DB7093',
			papayawhip: '#FFEFD5',
			peachpuff: '#FFDAB9',
			peru: '#CD853F',
			pink: '#FFC0CB',
			plum: '#DDA0DD',
			powderblue: '#B0E0E6',
			rosybrown: '#BC8F8F',
			royalblue: '#4169E1',
			saddlebrown: '#8B4513',
			salmon: '#FA8072',
			sandybrown: '#F4A460',
			seagreen: '#2E8B57',
			seashell: '#FFF5EE',
			sienna: '#A0522D',
			skyblue: '#87CEEB',
			slateblue: '#6A5ACD',
			slategray: '#708090',
			slategrey: '#708090',
			snow: '#FFFAFA',
			springgreen: '#00FF7F',
			steelblue: '#4682B4',
			tan: '#D2B48C',
			thistle: '#D8BFD8',
			tomato: '#FF6347',
			turquoise: '#40E0D0',
			violet: '#EE82EE',
			wheat: '#F5DEB3',
			whitesmoke: '#F5F5F5',
			yellowgreen: '#9ACD32'
		};


		function getRgbHslContent(styleString) {
			var start = styleString.indexOf('(', 3);
			var end = styleString.indexOf(')', start + 1);
			var parts = styleString.substring(start + 1, end).split(',');
			// add alpha if needed
			if (parts.length != 4 || styleString.charAt(3) != 'a') {
				parts[3] = 1;
			}
			return parts;
		}

		function percent(s) {
			return parseFloat(s) / 100;
		}

		function clamp(v, min, max) {
			return Math.min(max, Math.max(min, v));
		}

		function hslToRgb(parts) {
			var r, g, b, h, s, l;
			h = parseFloat(parts[0]) / 360 % 360;
			if (h < 0)
				h++;
			s = clamp(percent(parts[1]), 0, 1);
			l = clamp(percent(parts[2]), 0, 1);
			if (s == 0) {
				r = g = b = l; // achromatic
			} else {
				var q = l < 0.5 ? l * (1 + s) : l + s - l * s;
				var p = 2 * l - q;
				r = hueToRgb(p, q, h + 1 / 3);
				g = hueToRgb(p, q, h);
				b = hueToRgb(p, q, h - 1 / 3);
			}

			return '#' + decToHex[Math.floor(r * 255)] +
				decToHex[Math.floor(g * 255)] +
				decToHex[Math.floor(b * 255)];
		}

		function hueToRgb(m1, m2, h) {
			if (h < 0)
				h++;
			if (h > 1)
				h--;

			if (6 * h < 1)
				return m1 + (m2 - m1) * 6 * h;
			else if (2 * h < 1)
				return m2;
			else if (3 * h < 2)
				return m1 + (m2 - m1) * (2 / 3 - h) * 6;
			else
				return m1;
		}

		var processStyleCache = {};

		function processStyle(styleString) {
			if (styleString in processStyleCache) {
				return processStyleCache[styleString];
			}

			var str, alpha = 1;

			styleString = String(styleString);
			if (styleString.charAt(0) == '#') {
				str = styleString;
			} else if (/^rgb/.test(styleString)) {
				var parts = getRgbHslContent(styleString);
				var str = '#',
					n;
				for (var i = 0; i < 3; i++) {
					if (parts[i].indexOf('%') != -1) {
						n = Math.floor(percent(parts[i]) * 255);
					} else {
						n = +parts[i];
					}
					str += decToHex[clamp(n, 0, 255)];
				}
				alpha = +parts[3];
			} else if (/^hsl/.test(styleString)) {
				var parts = getRgbHslContent(styleString);
				str = hslToRgb(parts);
				alpha = parts[3];
			} else {
				str = colorData[styleString] || styleString;
			}
			return processStyleCache[styleString] = {
				color: str,
				alpha: alpha
			};
		}

		var DEFAULT_STYLE = {
			style: 'normal',
			variant: 'normal',
			weight: 'normal',
			size: 10,
			family: 'sans-serif'
		};

		// Internal text style cache
		var fontStyleCache = {};

		function processFontStyle(styleString) {
			if (fontStyleCache[styleString]) {
				return fontStyleCache[styleString];
			}

			var el = document.createElement('div');
			var style = el.style;
			try {
				style.font = styleString;
			} catch (ex) {
				// Ignore failures to set to invalid font.
			}

			return fontStyleCache[styleString] = {
				style: style.fontStyle || DEFAULT_STYLE.style,
				variant: style.fontVariant || DEFAULT_STYLE.variant,
				weight: style.fontWeight || DEFAULT_STYLE.weight,
				size: style.fontSize || DEFAULT_STYLE.size,
				family: style.fontFamily || DEFAULT_STYLE.family
			};
		}

		function getComputedStyle(style, element) {
			var computedStyle = {};

			for (var p in style) {
				computedStyle[p] = style[p];
			}

			// Compute the size
			var canvasFontSize = parseFloat(element.currentStyle.fontSize),
				fontSize = parseFloat(style.size);

			if (typeof style.size == 'number') {
				computedStyle.size = style.size;
			} else if (style.size.indexOf('px') != -1) {
				computedStyle.size = fontSize;
			} else if (style.size.indexOf('em') != -1) {
				computedStyle.size = canvasFontSize * fontSize;
			} else if (style.size.indexOf('%') != -1) {
				computedStyle.size = (canvasFontSize / 100) * fontSize;
			} else if (style.size.indexOf('pt') != -1) {
				computedStyle.size = fontSize / .75;
			} else {
				computedStyle.size = canvasFontSize;
			}

			// Different scaling between normal text and VML text. This was found using
			// trial and error to get the same size as non VML text.
			computedStyle.size *= 0.981;

			return computedStyle;
		}

		function buildStyle(style) {
			return style.style + ' ' + style.variant + ' ' + style.weight + ' ' +
				style.size + 'px ' + style.family;
		}

		var lineCapMap = {
			'butt': 'flat',
			'round': 'round'
		};

		function processLineCap(lineCap) {
			return lineCapMap[lineCap] || 'square';
		}

		/**
		 * This class implements CanvasRenderingContext2D interface as described by
		 * the WHATWG.
		 * @param {HTMLElement} canvasElement The element that the 2D context should
		 * be associated with
		 */
		function CanvasRenderingContext2D_(canvasElement) {
			this.m_ = createMatrixIdentity();

			this.mStack_ = [];
			this.aStack_ = [];
			this.currentPath_ = [];

			// Canvas context properties
			this.strokeStyle = '#000';
			this.fillStyle = '#000';

			this.lineWidth = 1;
			this.lineJoin = 'miter';
			this.lineCap = 'butt';
			this.miterLimit = Z * 1;
			this.globalAlpha = 1;
			this.font = '10px sans-serif';
			this.textAlign = 'left';
			this.textBaseline = 'alphabetic';
			this.canvas = canvasElement;

			var cssText = 'width:' + canvasElement.clientWidth + 'px;height:' +
				canvasElement.clientHeight + 'px;overflow:hidden;position:absolute';
			var el = canvasElement.ownerDocument.createElement('div');
			el.style.cssText = cssText;
			canvasElement.appendChild(el);

			var overlayEl = el.cloneNode(false);
			// Use a non transparent background.
			overlayEl.style.backgroundColor = 'red';
			overlayEl.style.filter = 'alpha(opacity=0)';
			canvasElement.appendChild(overlayEl);

			this.element_ = el;
			this.arcScaleX_ = 1;
			this.arcScaleY_ = 1;
			this.lineScale_ = 1;
		}

		var contextPrototype = CanvasRenderingContext2D_.prototype;
		contextPrototype.clearRect = function () {
			if (this.textMeasureEl_) {
				this.textMeasureEl_.removeNode(true);
				this.textMeasureEl_ = null;
			}
			this.element_.innerHTML = '';
		};

		contextPrototype.beginPath = function () {
			// TODO: Branch current matrix so that save/restore has no effect
			//       as per safari docs.
			this.currentPath_ = [];
		};

		contextPrototype.moveTo = function (aX, aY) {
			var p = getCoords(this, aX, aY);
			this.currentPath_.push({
				type: 'moveTo',
				x: p.x,
				y: p.y
			});
			this.currentX_ = p.x;
			this.currentY_ = p.y;
		};

		contextPrototype.lineTo = function (aX, aY) {
			var p = getCoords(this, aX, aY);
			this.currentPath_.push({
				type: 'lineTo',
				x: p.x,
				y: p.y
			});

			this.currentX_ = p.x;
			this.currentY_ = p.y;
		};

		contextPrototype.bezierCurveTo = function (aCP1x, aCP1y,
			aCP2x, aCP2y,
			aX, aY) {
			var p = getCoords(this, aX, aY);
			var cp1 = getCoords(this, aCP1x, aCP1y);
			var cp2 = getCoords(this, aCP2x, aCP2y);
			bezierCurveTo(this, cp1, cp2, p);
		};

		// Helper function that takes the already fixed cordinates.
		function bezierCurveTo(self, cp1, cp2, p) {
			self.currentPath_.push({
				type: 'bezierCurveTo',
				cp1x: cp1.x,
				cp1y: cp1.y,
				cp2x: cp2.x,
				cp2y: cp2.y,
				x: p.x,
				y: p.y
			});
			self.currentX_ = p.x;
			self.currentY_ = p.y;
		}

		contextPrototype.quadraticCurveTo = function (aCPx, aCPy, aX, aY) {
			// the following is lifted almost directly from
			// http://developer.mozilla.org/en/docs/Canvas_tutorial:Drawing_shapes

			var cp = getCoords(this, aCPx, aCPy);
			var p = getCoords(this, aX, aY);

			var cp1 = {
				x: this.currentX_ + 2.0 / 3.0 * (cp.x - this.currentX_),
				y: this.currentY_ + 2.0 / 3.0 * (cp.y - this.currentY_)
			};
			var cp2 = {
				x: cp1.x + (p.x - this.currentX_) / 3.0,
				y: cp1.y + (p.y - this.currentY_) / 3.0
			};

			bezierCurveTo(this, cp1, cp2, p);
		};

		contextPrototype.arc = function (aX, aY, aRadius,
			aStartAngle, aEndAngle, aClockwise) {
			aRadius *= Z;
			var arcType = aClockwise ? 'at' : 'wa';

			var xStart = aX + mc(aStartAngle) * aRadius - Z2;
			var yStart = aY + ms(aStartAngle) * aRadius - Z2;

			var xEnd = aX + mc(aEndAngle) * aRadius - Z2;
			var yEnd = aY + ms(aEndAngle) * aRadius - Z2;

			// IE won't render arches drawn counter clockwise if xStart == xEnd.
			if (xStart == xEnd && !aClockwise) {
				xStart += 0.125; // Offset xStart by 1/80 of a pixel. Use something
				// that can be represented in binary
			}

			var p = getCoords(this, aX, aY);
			var pStart = getCoords(this, xStart, yStart);
			var pEnd = getCoords(this, xEnd, yEnd);

			this.currentPath_.push({
				type: arcType,
				x: p.x,
				y: p.y,
				radius: aRadius,
				xStart: pStart.x,
				yStart: pStart.y,
				xEnd: pEnd.x,
				yEnd: pEnd.y
			});

		};

		contextPrototype.rect = function (aX, aY, aWidth, aHeight) {
			this.moveTo(aX, aY);
			this.lineTo(aX + aWidth, aY);
			this.lineTo(aX + aWidth, aY + aHeight);
			this.lineTo(aX, aY + aHeight);
			this.closePath();
		};

		contextPrototype.strokeRect = function (aX, aY, aWidth, aHeight) {
			var oldPath = this.currentPath_;
			this.beginPath();

			this.moveTo(aX, aY);
			this.lineTo(aX + aWidth, aY);
			this.lineTo(aX + aWidth, aY + aHeight);
			this.lineTo(aX, aY + aHeight);
			this.closePath();
			this.stroke();

			this.currentPath_ = oldPath;
		};

		contextPrototype.fillRect = function (aX, aY, aWidth, aHeight) {
			var oldPath = this.currentPath_;
			this.beginPath();

			this.moveTo(aX, aY);
			this.lineTo(aX + aWidth, aY);
			this.lineTo(aX + aWidth, aY + aHeight);
			this.lineTo(aX, aY + aHeight);
			this.closePath();
			this.fill();

			this.currentPath_ = oldPath;
		};

		contextPrototype.createLinearGradient = function (aX0, aY0, aX1, aY1) {
			var gradient = new CanvasGradient_('gradient');
			gradient.x0_ = aX0;
			gradient.y0_ = aY0;
			gradient.x1_ = aX1;
			gradient.y1_ = aY1;
			return gradient;
		};

		contextPrototype.createRadialGradient = function (aX0, aY0, aR0,
			aX1, aY1, aR1) {
			var gradient = new CanvasGradient_('gradientradial');
			gradient.x0_ = aX0;
			gradient.y0_ = aY0;
			gradient.r0_ = aR0;
			gradient.x1_ = aX1;
			gradient.y1_ = aY1;
			gradient.r1_ = aR1;
			return gradient;
		};

		contextPrototype.drawImage = function (image, var_args) {
			var dx, dy, dw, dh, sx, sy, sw, sh;

			// to find the original width we overide the width and height
			var oldRuntimeWidth = image.runtimeStyle.width;
			var oldRuntimeHeight = image.runtimeStyle.height;
			image.runtimeStyle.width = 'auto';
			image.runtimeStyle.height = 'auto';

			// get the original size
			var w = image.width;
			var h = image.height;

			// and remove overides
			image.runtimeStyle.width = oldRuntimeWidth;
			image.runtimeStyle.height = oldRuntimeHeight;

			if (arguments.length == 3) {
				dx = arguments[1];
				dy = arguments[2];
				sx = sy = 0;
				sw = dw = w;
				sh = dh = h;
			} else if (arguments.length == 5) {
				dx = arguments[1];
				dy = arguments[2];
				dw = arguments[3];
				dh = arguments[4];
				sx = sy = 0;
				sw = w;
				sh = h;
			} else if (arguments.length == 9) {
				sx = arguments[1];
				sy = arguments[2];
				sw = arguments[3];
				sh = arguments[4];
				dx = arguments[5];
				dy = arguments[6];
				dw = arguments[7];
				dh = arguments[8];
			} else {
				throw Error('Invalid number of arguments');
			}

			var d = getCoords(this, dx, dy);

			var w2 = sw / 2;
			var h2 = sh / 2;

			var vmlStr = [];

			var W = 10;
			var H = 10;

			// For some reason that I've now forgotten, using divs didn't work
			vmlStr.push(' <g_vml_:group',
				' coordsize="', Z * W, ',', Z * H, '"',
				' coordorigin="0,0"',
				' style="width:', W, 'px;height:', H, 'px;position:absolute;');

			// If filters are necessary (rotation exists), create them
			// filters are bog-slow, so only create them if abbsolutely necessary
			// The following check doesn't account for skews (which don't exist
			// in the canvas spec (yet) anyway.

			if (this.m_[0][0] != 1 || this.m_[0][1] ||
				this.m_[1][1] != 1 || this.m_[1][0]) {
				var filter = [];

				// Note the 12/21 reversal
				filter.push('M11=', this.m_[0][0], ',',
					'M12=', this.m_[1][0], ',',
					'M21=', this.m_[0][1], ',',
					'M22=', this.m_[1][1], ',',
					'Dx=', mr(d.x / Z), ',',
					'Dy=', mr(d.y / Z), '');

				// Bounding box calculation (need to minimize displayed area so that
				// filters don't waste time on unused pixels.
				var max = d;
				var c2 = getCoords(this, dx + dw, dy);
				var c3 = getCoords(this, dx, dy + dh);
				var c4 = getCoords(this, dx + dw, dy + dh);

				max.x = m.max(max.x, c2.x, c3.x, c4.x);
				max.y = m.max(max.y, c2.y, c3.y, c4.y);

				vmlStr.push('padding:0 ', mr(max.x / Z), 'px ', mr(max.y / Z),
					'px 0;filter:progid:DXImageTransform.Microsoft.Matrix(',
					filter.join(''), ", sizingmethod='clip');");

			} else {
				vmlStr.push('top:', mr(d.y / Z), 'px;left:', mr(d.x / Z), 'px;');
			}

			vmlStr.push(' ">',
				'<g_vml_:image src="', image.src, '"',
				' style="width:', Z * dw, 'px;',
				' height:', Z * dh, 'px"',
				' cropleft="', sx / w, '"',
				' croptop="', sy / h, '"',
				' cropright="', (w - sx - sw) / w, '"',
				' cropbottom="', (h - sy - sh) / h, '"',
				' />',
				'</g_vml_:group>');

			this.element_.insertAdjacentHTML('BeforeEnd', vmlStr.join(''));
		};

		contextPrototype.stroke = function (aFill) {
			var lineStr = [];
			var lineOpen = false;

			var W = 10;
			var H = 10;

			lineStr.push('<g_vml_:shape',
				' filled="', !! aFill, '"',
				' style="position:absolute;width:', W, 'px;height:', H, 'px;"',
				' coordorigin="0,0"',
				' coordsize="', Z * W, ',', Z * H, '"',
				' stroked="', !aFill, '"',
				' path="');

			var newSeq = false;
			var min = {
				x: null,
				y: null
			};
			var max = {
				x: null,
				y: null
			};

			for (var i = 0; i < this.currentPath_.length; i++) {
				var p = this.currentPath_[i];
				var c;

				switch (p.type) {
				case 'moveTo':
					c = p;
					lineStr.push(' m ', mr(p.x), ',', mr(p.y));
					break;
				case 'lineTo':
					lineStr.push(' l ', mr(p.x), ',', mr(p.y));
					break;
				case 'close':
					lineStr.push(' x ');
					p = null;
					break;
				case 'bezierCurveTo':
					lineStr.push(' c ',
						mr(p.cp1x), ',', mr(p.cp1y), ',',
						mr(p.cp2x), ',', mr(p.cp2y), ',',
						mr(p.x), ',', mr(p.y));
					break;
				case 'at':
				case 'wa':
					lineStr.push(' ', p.type, ' ',
						mr(p.x - this.arcScaleX_ * p.radius), ',',
						mr(p.y - this.arcScaleY_ * p.radius), ' ',
						mr(p.x + this.arcScaleX_ * p.radius), ',',
						mr(p.y + this.arcScaleY_ * p.radius), ' ',
						mr(p.xStart), ',', mr(p.yStart), ' ',
						mr(p.xEnd), ',', mr(p.yEnd));
					break;
				}


				// TODO: Following is broken for curves due to
				//       move to proper paths.

				// Figure out dimensions so we can do gradient fills
				// properly
				if (p) {
					if (min.x == null || p.x < min.x) {
						min.x = p.x;
					}
					if (max.x == null || p.x > max.x) {
						max.x = p.x;
					}
					if (min.y == null || p.y < min.y) {
						min.y = p.y;
					}
					if (max.y == null || p.y > max.y) {
						max.y = p.y;
					}
				}
			}
			lineStr.push(' ">');

			if (!aFill) {
				appendStroke(this, lineStr);
			} else {
				appendFill(this, lineStr, min, max);
			}

			lineStr.push('</g_vml_:shape>');

			this.element_.insertAdjacentHTML('beforeEnd', lineStr.join(''));
		};

		function appendStroke(ctx, lineStr) {
			var a = processStyle(ctx.strokeStyle);
			var color = a.color;
			var opacity = a.alpha * ctx.globalAlpha;
			var lineWidth = ctx.lineScale_ * ctx.lineWidth;

			// VML cannot correctly render a line if the width is less than 1px.
			// In that case, we dilute the color to make the line look thinner.
			if (lineWidth < 1) {
				opacity *= lineWidth;
			}

			lineStr.push(
				'<g_vml_:stroke',
				' opacity="', opacity, '"',
				' joinstyle="', ctx.lineJoin, '"',
				' miterlimit="', ctx.miterLimit, '"',
				' endcap="', processLineCap(ctx.lineCap), '"',
				' weight="', lineWidth, 'px"',
				' color="', color, '" />'
			);
		}

		function appendFill(ctx, lineStr, min, max) {
			var fillStyle = ctx.fillStyle;
			var arcScaleX = ctx.arcScaleX_;
			var arcScaleY = ctx.arcScaleY_;
			var width = max.x - min.x;
			var height = max.y - min.y;
			if (fillStyle instanceof CanvasGradient_) {
				// TODO: Gradients transformed with the transformation matrix.
				var angle = 0;
				var focus = {
					x: 0,
					y: 0
				};

				// additional offset
				var shift = 0;
				// scale factor for offset
				var expansion = 1;

				if (fillStyle.type_ == 'gradient') {
					var x0 = fillStyle.x0_ / arcScaleX;
					var y0 = fillStyle.y0_ / arcScaleY;
					var x1 = fillStyle.x1_ / arcScaleX;
					var y1 = fillStyle.y1_ / arcScaleY;
					var p0 = getCoords(ctx, x0, y0);
					var p1 = getCoords(ctx, x1, y1);
					var dx = p1.x - p0.x;
					var dy = p1.y - p0.y;
					angle = Math.atan2(dx, dy) * 180 / Math.PI;

					// The angle should be a non-negative number.
					if (angle < 0) {
						angle += 360;
					}

					// Very small angles produce an unexpected result because they are
					// converted to a scientific notation string.
					if (angle < 1e-6) {
						angle = 0;
					}
				} else {
					var p0 = getCoords(ctx, fillStyle.x0_, fillStyle.y0_);
					focus = {
						x: (p0.x - min.x) / width,
						y: (p0.y - min.y) / height
					};

					width /= arcScaleX * Z;
					height /= arcScaleY * Z;
					var dimension = m.max(width, height);
					shift = 2 * fillStyle.r0_ / dimension;
					expansion = 2 * fillStyle.r1_ / dimension - shift;
				}

				// We need to sort the color stops in ascending order by offset,
				// otherwise IE won't interpret it correctly.
				var stops = fillStyle.colors_;
				stops.sort(function (cs1, cs2) {
					return cs1.offset - cs2.offset;
				});

				var length = stops.length;
				var color1 = stops[0].color;
				var color2 = stops[length - 1].color;
				var opacity1 = stops[0].alpha * ctx.globalAlpha;
				var opacity2 = stops[length - 1].alpha * ctx.globalAlpha;

				var colors = [];
				for (var i = 0; i < length; i++) {
					var stop = stops[i];
					colors.push(stop.offset * expansion + shift + ' ' + stop.color);
				}

				// When colors attribute is used, the meanings of opacity and o:opacity2
				// are reversed.
				lineStr.push('<g_vml_:fill type="', fillStyle.type_, '"',
					' method="none" focus="100%"',
					' color="', color1, '"',
					' color2="', color2, '"',
					' colors="', colors.join(','), '"',
					' opacity="', opacity2, '"',
					' g_o_:opacity2="', opacity1, '"',
					' angle="', angle, '"',
					' focusposition="', focus.x, ',', focus.y, '" />');
			} else if (fillStyle instanceof CanvasPattern_) {
				if (width && height) {
					var deltaLeft = -min.x;
					var deltaTop = -min.y;
					lineStr.push('<g_vml_:fill',
						' position="',
						deltaLeft / width * arcScaleX * arcScaleX, ',',
						deltaTop / height * arcScaleY * arcScaleY, '"',
						' type="tile"',
						// TODO: Figure out the correct size to fit the scale.
						//' size="', w, 'px ', h, 'px"',
						' src="', fillStyle.src_, '" />');
				}
			} else {
				var a = processStyle(ctx.fillStyle);
				var color = a.color;
				var opacity = a.alpha * ctx.globalAlpha;
				lineStr.push('<g_vml_:fill color="', color, '" opacity="', opacity,
					'" />');
			}
		}

		contextPrototype.fill = function () {
			this.stroke(true);
		};

		contextPrototype.closePath = function () {
			this.currentPath_.push({
				type: 'close'
			});
		};

		function getCoords(ctx, aX, aY) {
			var m = ctx.m_;
			return {
				x: Z * (aX * m[0][0] + aY * m[1][0] + m[2][0]) - Z2,
				y: Z * (aX * m[0][1] + aY * m[1][1] + m[2][1]) - Z2
			};
		};

		contextPrototype.save = function () {
			var o = {};
			copyState(this, o);
			this.aStack_.push(o);
			this.mStack_.push(this.m_);
			this.m_ = matrixMultiply(createMatrixIdentity(), this.m_);
		};

		contextPrototype.restore = function () {
			if (this.aStack_.length) {
				copyState(this.aStack_.pop(), this);
				this.m_ = this.mStack_.pop();
			}
		};

		function matrixIsFinite(m) {
			return isFinite(m[0][0]) && isFinite(m[0][1]) &&
				isFinite(m[1][0]) && isFinite(m[1][1]) &&
				isFinite(m[2][0]) && isFinite(m[2][1]);
		}

		function setM(ctx, m, updateLineScale) {
			if (!matrixIsFinite(m)) {
				return;
			}
			ctx.m_ = m;

			if (updateLineScale) {
				// Get the line scale.
				// Determinant of this.m_ means how much the area is enlarged by the
				// transformation. So its square root can be used as a scale factor
				// for width.
				var det = m[0][0] * m[1][1] - m[0][1] * m[1][0];
				ctx.lineScale_ = sqrt(abs(det));
			}
		}

		contextPrototype.translate = function (aX, aY) {
			var m1 = [
      [1, 0, 0],
      [0, 1, 0],
      [aX, aY, 1]
    ];

			setM(this, matrixMultiply(m1, this.m_), false);
		};

		contextPrototype.rotate = function (aRot) {
			var c = mc(aRot);
			var s = ms(aRot);

			var m1 = [
      [c, s, 0],
      [-s, c, 0],
      [0, 0, 1]
    ];

			setM(this, matrixMultiply(m1, this.m_), false);
		};

		contextPrototype.scale = function (aX, aY) {
			this.arcScaleX_ *= aX;
			this.arcScaleY_ *= aY;
			var m1 = [
      [aX, 0, 0],
      [0, aY, 0],
      [0, 0, 1]
    ];

			setM(this, matrixMultiply(m1, this.m_), true);
		};

		contextPrototype.transform = function (m11, m12, m21, m22, dx, dy) {
			var m1 = [
      [m11, m12, 0],
      [m21, m22, 0],
      [dx, dy, 1]
    ];

			setM(this, matrixMultiply(m1, this.m_), true);
		};

		contextPrototype.setTransform = function (m11, m12, m21, m22, dx, dy) {
			var m = [
      [m11, m12, 0],
      [m21, m22, 0],
      [dx, dy, 1]
    ];

			setM(this, m, true);
		};

		/**
		 * The text drawing function.
		 * The maxWidth argument isn't taken in account, since no browser supports
		 * it yet.
		 */
		contextPrototype.drawText_ = function (text, x, y, maxWidth, stroke) {
			var m = this.m_,
				delta = 1000,
				left = 0,
				right = delta,
				offset = {
					x: 0,
					y: 0
				},
				lineStr = [];

			var fontStyle = getComputedStyle(processFontStyle(this.font),
				this.element_);

			var fontStyleString = buildStyle(fontStyle);

			var elementStyle = this.element_.currentStyle;
			var textAlign = this.textAlign.toLowerCase();
			switch (textAlign) {
			case 'left':
			case 'center':
			case 'right':
				break;
			case 'end':
				textAlign = elementStyle.direction == 'ltr' ? 'right' : 'left';
				break;
			case 'start':
				textAlign = elementStyle.direction == 'rtl' ? 'right' : 'left';
				break;
			default:
				textAlign = 'left';
			}

			// 1.75 is an arbitrary number, as there is no info about the text baseline
			switch (this.textBaseline) {
			case 'hanging':
			case 'top':
				offset.y = fontStyle.size / 1.75;
				break;
			case 'middle':
				break;
			default:
			case null:
			case 'alphabetic':
			case 'ideographic':
			case 'bottom':
				offset.y = -fontStyle.size / 2.25;
				break;
			}

			switch (textAlign) {
			case 'right':
				left = delta;
				right = 0.05;
				break;
			case 'center':
				left = right = delta / 2;
				break;
			}

			var d = getCoords(this, x + offset.x, y + offset.y);

			lineStr.push('<g_vml_:line from="', -left, ' 0" to="', right, ' 0.05" ',
				' coordsize="100 100" coordorigin="0 0"',
				' filled="', !stroke, '" stroked="', !! stroke,
				'" style="position:absolute;width:1px;height:1px;">');

			if (stroke) {
				appendStroke(this, lineStr);
			} else {
				// TODO: Fix the min and max params.
				appendFill(this, lineStr, {
					x: -left,
					y: 0
				}, {
					x: right,
					y: fontStyle.size
				});
			}

			var skewM = m[0][0].toFixed(3) + ',' + m[1][0].toFixed(3) + ',' +
				m[0][1].toFixed(3) + ',' + m[1][1].toFixed(3) + ',0,0';

			var skewOffset = mr(d.x / Z) + ',' + mr(d.y / Z);

			lineStr.push('<g_vml_:skew on="t" matrix="', skewM, '" ',
				' offset="', skewOffset, '" origin="', left, ' 0" />',
				'<g_vml_:path textpathok="true" />',
				'<g_vml_:textpath on="true" string="',
				encodeHtmlAttribute(text),
				'" style="v-text-align:', textAlign,
				';font:', encodeHtmlAttribute(fontStyleString),
				'" /></g_vml_:line>');

			this.element_.insertAdjacentHTML('beforeEnd', lineStr.join(''));
		};

		contextPrototype.fillText = function (text, x, y, maxWidth) {
			this.drawText_(text, x, y, maxWidth, false);
		};

		contextPrototype.strokeText = function (text, x, y, maxWidth) {
			this.drawText_(text, x, y, maxWidth, true);
		};

		contextPrototype.measureText = function (text) {
			if (!this.textMeasureEl_) {
				var s = '<span style="position:absolute;' +
					'top:-20000px;left:0;padding:0;margin:0;border:none;' +
					'white-space:pre;"></span>';
				this.element_.insertAdjacentHTML('beforeEnd', s);
				this.textMeasureEl_ = this.element_.lastChild;
			}
			var doc = this.element_.ownerDocument;
			this.textMeasureEl_.innerHTML = '';
			this.textMeasureEl_.style.font = this.font;
			// Don't use innerHTML or innerText because they allow markup/whitespace.
			this.textMeasureEl_.appendChild(doc.createTextNode(text));
			return {
				width: this.textMeasureEl_.offsetWidth
			};
		};

		/******** STUBS ********/
		contextPrototype.clip = function () {
			// TODO: Implement
		};

		contextPrototype.arcTo = function () {
			// TODO: Implement
		};

		contextPrototype.createPattern = function (image, repetition) {
			return new CanvasPattern_(image, repetition);
		};

		// Gradient / Pattern Stubs
		function CanvasGradient_(aType) {
			this.type_ = aType;
			this.x0_ = 0;
			this.y0_ = 0;
			this.r0_ = 0;
			this.x1_ = 0;
			this.y1_ = 0;
			this.r1_ = 0;
			this.colors_ = [];
		}

		CanvasGradient_.prototype.addColorStop = function (aOffset, aColor) {
			aColor = processStyle(aColor);
			this.colors_.push({
				offset: aOffset,
				color: aColor.color,
				alpha: aColor.alpha
			});
		};

		function CanvasPattern_(image, repetition) {
			assertImageIsValid(image);
			switch (repetition) {
			case 'repeat':
			case null:
			case '':
				this.repetition_ = 'repeat';
				break
			case 'repeat-x':
			case 'repeat-y':
			case 'no-repeat':
				this.repetition_ = repetition;
				break;
			default:
				throwException('SYNTAX_ERR');
			}

			this.src_ = image.src;
			this.width_ = image.width;
			this.height_ = image.height;
		}

		function throwException(s) {
			throw new DOMException_(s);
		}

		function assertImageIsValid(img) {
			if (!img || img.nodeType != 1 || img.tagName != 'IMG') {
				throwException('TYPE_MISMATCH_ERR');
			}
			if (img.readyState != 'complete') {
				throwException('INVALID_STATE_ERR');
			}
		}

		function DOMException_(s) {
			this.code = this[s];
			this.message = s + ': DOM Exception ' + this.code;
		}
		var p = DOMException_.prototype = new Error;
		p.INDEX_SIZE_ERR = 1;
		p.DOMSTRING_SIZE_ERR = 2;
		p.HIERARCHY_REQUEST_ERR = 3;
		p.WRONG_DOCUMENT_ERR = 4;
		p.INVALID_CHARACTER_ERR = 5;
		p.NO_DATA_ALLOWED_ERR = 6;
		p.NO_MODIFICATION_ALLOWED_ERR = 7;
		p.NOT_FOUND_ERR = 8;
		p.NOT_SUPPORTED_ERR = 9;
		p.INUSE_ATTRIBUTE_ERR = 10;
		p.INVALID_STATE_ERR = 11;
		p.SYNTAX_ERR = 12;
		p.INVALID_MODIFICATION_ERR = 13;
		p.NAMESPACE_ERR = 14;
		p.INVALID_ACCESS_ERR = 15;
		p.VALIDATION_ERR = 16;
		p.TYPE_MISMATCH_ERR = 17;

		// set up externs
		G_vmlCanvasManager = G_vmlCanvasManager_;
		CanvasRenderingContext2D = CanvasRenderingContext2D_;
		CanvasGradient = CanvasGradient_;
		CanvasPattern = CanvasPattern_;
		DOMException = DOMException_;
	})();

} // if